Download auditory profiling and hearing-aid satisfaction in hearing

Dan Med J 63/10 October 2016
d a n i s h m E d i c a l J O U R NAL 1
Auditory profiling and hearing-aid satisfaction
in hearing-aid candidates
Nicoline Thorup1, Sébastien Santurette1, 2, Søren Jørgensen2, Erik Kjærbøl1, Torsten Dau2 & Morten Friis3
ABSTRACT
INTRODUCTION: Hearing-impaired (HI) listeners often com-
plain about difficulties communicating in the presence of
background noise, although audibility may be restored by a
hearing-aid (HA). The audiogram typically forms the basis
for HA fitting, i.e. people with similar audiograms are given
the same prescription by default. This study aimed at iden­
tifying clinically relevant tests that may serve as an informative addition to the audiogram and which may relate more
directly to HA satisfaction than the audiogram does.
METHODS: A total of 29 HI and 26 normal-hearing listeners
performed tests of spectral and temporal resolution, bin­
aural hearing, speech intelligibility in stationary and fluctuating noise and a working-memory test. Six weeks after HA
fitting, the HI listeners answered a questionnaire evaluating
HA treatment.
RESULTS: No other measures than masking release between
fluctuating and stationary noise correlated significantly with
audibility. The HI listeners who obtained the least advantage from fluctuations in background noise in terms of
speech intelligibility experienced greater HA satisfaction.
CONCLUSION: HI listeners have difficulties in different hearing domains that are not predictable from their audiogram.
Measures of temporal resolution or speech perception in
both stationary and fluctuating noise could be relevant
measures to consider in an extended auditory profile.
FUNDING: The study was supported by Grosserer L.F. Foghts
Fond.
TRIAL REGISTRATION: The protocol was approved by the
Science Ethics Committee of the Capital Region of Denmark
(reference H-3-2013-004).
It has been estimated that 30% of Danish hearing-aid
(HA) users found that listening situations improved only
moderately, slightly or not at all after HA prescription
[1], suggesting inadequate HA treatment. Pure-tone audiometry typically forms the basis for providing and fitting HA devices. Patients with the same audiometric
profile may therefore experience differences in HA satisfaction.
Although audibility may be restored by a HA, users
often complain about communicating in the presence of
background noise. The audiogram has been found to
correlate well with speech intelligibility in quiet, but to
correlate poorly in noisy contexts [2, 3]. Moreover, hear-
ing-impaired (HI) listeners with normal or near-normal
low-frequency pure-tone hearing thresholds may show
speech identification deficits when the speech spectrum
is limited to regions of normal or near-normal hearing
[4]. Speech intelligibility in noise has also been found to
correlate with temporal fine-structure (TFS) processing
abilities reflected by, e.g., frequency discrimination [2,
5]; and TFS processing deficits can be present despite
near-normal thresholds [6]. The evaluation of a test battery including different hearing domains has also shown
that HI listeners can suffer from auditory deficits that do
not necessarily correlate with the audiogram [7].
Despite compelling evidence that the audiogram
alone does not sufficiently characterise hearing loss, it
remains unclear which additional properties of hearing
function should be assessed in the clinic to provide ad­
equate HA rehabilitation. The aim of the present study
was to evaluate whether a clinical auditory profile including different psychoacoustic and cognitive tests
adds relevant information to the audiogram. The audi­
tory domains of interest were spectral and temporal
reso­lution, TFS processing and speech perception in
noise. Another aim was to evaluate HA satisfaction in relation to the auditory profile to investigate if specific test
outcomes relate to HA satisfaction.
METHODS
Listeners
A total of 29 HI listeners (aged 52-80 years, mean age
68.4 years, 13 females, eight new and 21 experienced
HA users) and 26 listeners with near-normal hearing
thresholds (NHT listeners; aged 41-70 years, mean age
55.8 years, 18 females) participated. The term “nearnormal” reflects the fact that thresholds were elevated
in some listeners at high frequencies. The NHT group
was included to obtain profile outcomes for a population in a similar age range but without hearing-sensitiv­
ity difficulties, and to observe the extent of individual
differences within this group. Figure 1 shows mean
audio­grams for the two groups.
Experimental set-up
All measurements were conducted via a PC in a soundproof booth. The stimuli were generated in MATLAB and
presented via a Fireface UCX sound card. For audiomet-
Original
article
1) Department of
Otorhinolaryngology,
Head and Neck Surgery
& Audiology,
Rigshospitalet
2) Hearing Systems,
Department of
Electrical Engineering,
Technical University of
Denmark
3) Department of
Otorhinolaryngology
and Audiology,
Aleris-Hamlet
Hospitals, Denmark
Dan Med J
2016;63(10):A5275
  2 d a n i s h m E d i c a l J O U R NAL
Dan Med J 63/10 October 2016
FigurE 1
Characterisation of participants. Mean pure-tone hearing-thresholds for
all hearing-impaired (HI) and near-normal hearing thresholds (NHT) listeners. Error bars shows the standard deviation for the respective frequency. HI listeners: The inclusion criteria were sensorineural high-frequency hearing loss, bilateral hearing-aid therapy, age of 18-80 years,
and Danish native language; the exclusion criteria were threshold asymmetry > 15 dB hearing level, asymmetry in speech discrimination > 20%,
or conductive hearing loss. NHT listeners: The inclusion criteria were
pure-tone average < 20 dB hearing level at 0.5, 1, and 1.5 kHz; pure-tone
average < 30 dB hearing level at 2, 3, and 4 kHz, age of 18-80 years, and
Danish native language; the exclusion criteria were threshold asymmetry
> 15 dB hearing level or asymmetry in speech discrimination > 20%.
Hearing threshold, dB
0
20
40
60
80
0.25
HI left ear
0.5
HI right ear
1
2
4
6
Frequency, kHz, log scale
NHT left ear
NHT right ear
ric measurements, Interacoustics AC40 and AC440 connected to TDH39 headphones or Madsen Orbiter OB922
connected to HDA200 headphones were used. Insert
earphones (EAR 3A) were used in listeners with a small
auditory canal.
General procedure
For pre-examination, air and bone conduction pure-tone
thresholds from 250-8,000 Hz were measured. The test
battery was always scheduled for another day than the
day of the pre-examination and HA fitting. For NHT listeners, the pre-examination and the test battery were
conducted in one session. A standardised written and
verbal introduction was given prior to each test. All tests
contained a training run. The cognitive test was carried
out before the psychoacoustic measurements, the sequence of which was randomised. All auditory tests
were conducted without HA.
The test battery
A summary of the tests conducted and the corresponding outcome measures is given in Table 1. A brief description of all tests is provided below.
Reading span
The test was used to evaluate working memory storage
and processing [8]. The main task was to recall the first
or the final word in a sequence of sentences presented
visually on a screen. The remembered words were pronounced out loud. The experimenter registered the answers. The secondary task was to assess continuously if
each sentence was correct or absurd. A total of 54 sentences (27 correct and 27 absurd) were presented.
Combined spectral and temporal resolution
Auditory spectral and temporal resolutions were tested
using a modified version of the combined spectral and
temporal resolution (F&T) test [9]. The task was to detect a pulsed 275-ms tone at 500 Hz in the presence of
broadband threshold-equalising noise containing no
gap, a three-equivalent rectangular bandwidths wide
spectral gap around the centre frequency or a 50-ms
temporal gap. A test frequency of 500 Hz was chosen to
minimise the effect of elevated hearing thresholds on
the results, which are more likely at higher test fre­
quencies [7]. The noise level was fixed at 55 dB sound
pressure level (SPL). The tone level was varied adaptively
using a Békésy tracking method with a starting value of
70 dB SPL. Each condition was measured twice, mon­
aurally in both ears. The sequence of noise conditions
and ears was randomised.
Interaural-phase-difference detection
Binaural TFS processing was evaluated by measuring the
upper frequency limit for which an interaural-phase-difference (IPD) of 180° was detectable [10]. Good abilities
in binaural TFS processing are important for, e.g., sound
localisation. The task was to detect which of three stimulus intervals contained an IPD and thus sounded more
spacious than the other two intervals with no IPD. The
stimulus was a sinusoidal-amplitude-modulated puretone with a 40-Hz modulation rate and a modulation
depth of 1. The presentation level was 35 dB sensation
level relative to pure-tone hearing-thresholds in each
ear. The start frequency was 250 Hz and was changed
according to a two-up one-down rule in step-sizes of a
half, a fifth, and a tenth octave that decreased after
each lower reversal. Two thresholds were obtained per
listener.
Hearing-in-noise test
The speech recognition threshold in noise (SRTn) was
measured using Lists 1 and 2 from the Danish hearing-innoise test (HINT) [11]. The task was to repeat sentences
presented binaurally. The answer was registered as “correct” or “false” by the experimenter. The noise level was
fixed at 65 dB SPL. The first sentence was presented at
zero-dB speech-to-noise-ratio. The speech level was
d a n i s h m E d i c a l J O U R NAL 3
Dan Med J 63/10 October 2016
changed according to a one-up one-down rule. The SRTn
was the mean of speech levels in the 15 last sentences
minus the noise level. The SRTn was measured in two
different noise types: a stationary speech-shaped noise
and a fluctuating background, the International Speech
Test Signal. Condition and list order were randomised.
International outcome inventory – hearing-aid
Six weeks after HA fitting, the HI listeners received the
Danish international outcome inventory – hearing-aid
(IOI-HA) [12] to evaluate the HA intervention. It consists
of seven items divided into two subscales: one evaluating the introspective aspects of the HA treatment and
the other evaluating interaction with the surroundings.
According to a new revision of the Danish translation,
item 5 was omitted [13].
Statistical analysis
The Pearson correlation coefficient was calculated between all test outcomes and the low (0.25, 0.5, 1 kHz) or
high (2, 4, 6 kHz) pure-tone average (PTA). For the F&T
test, correlations were calculated between the masking
releases (MRs) and pure-tone hearing thresholds at 500
Hz after pooling the data from both ears. For the IPD detection and HINT, the average PTA from the right and
left ear was used in the correlation analysis. Fisher’s
transformation was used to calculate the confidence
interval (CI) for the correlation coefficient. Correlations
between test outcomes and the IOI-HA subscales were
obtained in the same manner.
Trial registration: The protocol was approved by the Science Ethics Committee of the Capital Region of Denmark
(reference H-3-2013-004).
RESULTS
Group differences
Figure 2 shows the auditory-profile test results for the HI
and NHT groups. No significant difference between HI
and NHT listeners was found in the reading span (RS)
test (Figure 2A). In the F&T test, no significant difference
in spectral MR was found between the two groups.
However, temporal MR was significantly higher (p <
0.001, Wilcoxon rank sum test) for NHT than for HI listeners (Figure 2B). There was no significant group difference in terms of the upper frequency limit for IPD detection (Figure 2C). Concerning the ability to take
advantage of fluctuating noise for speech understanding
in noise, the HINT MR (MRHINT) was significantly higher
(p < 0.001, Wilcoxon rank sum test) in NHT than in HI
listeners.
Test battery outcome correlations with the audiogram
Table 2 (upper rows) lists the correlation coefficient CIs
between measures from each test and the PTA at high
and low frequencies. Only MRHINT was significantly correlated to low-frequency PTA. Outcomes from the RS, F&T
and IPD detection tests were not correlated with audi­
bility.
Test battery outcome correlations with HA satisfaction
Table 2 (lower rows) lists the correlation coefficient CIs
between IOI-HA and all test outcomes. A significant
nega­tive correlation was found between MRHINT and the
introspection subscale, also when controlling for PTA, indicating that HI listeners who had only limited advantage from fluctuating noise experienced a greater HA
satisfaction. Neither audibility nor other test outcomes
were correlated with HA satisfaction.
Table 1
Tests included in the test battery and corresponding outcomes and interpretation of the outcomes.
Domain
Test
Outcome; unit
Interpretation
Audibility
Pure-tone hearing
thresholds
PTAlow: 0.25, 0.5, 1 kHz; dB HL
PTAhigh: 2, 4, 6 kHz; dB HL
–
Working memory
RS
Correct words; n
High number of recalled words indicates good working memory capacity
Spectral and temporal
resolution
F&T-test
MRspec: MR no gap vs. spectral gap; dB
MRtemp: MR no gap vs. temporal gap; dB
High release of masking indicates good ability in spectral and/or tem­
poral resolution
Binaural TFS processing
IPD detection
Upper frequency limit for IPD detection; Hz
High frequency limit indicates good TFS processing
Speech recognition in noise
Danish HINT
MRHINT: MR stationary vs. fluctuating noise; dB
High MR indicates good ability to make use of fluctuations in background
noise in terms of speech intelligibility
HA treatment evaluation
IOI-HA
Introspection subscale; score
Interaction subscale; score
Higher score indicates greater HA satisfaction
F&T = combined spectral and temporal resolution; HA = hearing-aid; high = high-frequency; HINT = hearing-in-noise test; HL = hearing level; IOI = international outcome inventory;
IPD = interaural-phase-difference; low = low-frequency; MR = masking release; PTA = pure-tone average; RS = reading span; spec = spectral; temp = temporal; TFS = temporal fine
structure.
  4 d a n i s h m E d i c a l J O U R NAL
Dan Med J 63/10 October 2016
FigurE 2
Box-plot test results for
reading span (A), combined spectral and temporal resolution test (B),
interaural phase difference (IPD) detection (C),
and hearing-in-noise test
(D) for hearing impaired
(HI)- and near-normal
hearing thresholds (NHT)
listeners. Median values
between 25th and 75th
percentiles and extension
to the most extreme data
points. Δ: comparison
intervals for medians: p
< 0.05 if the comparison
intervals do not overlap.
A: Correctly recalled words, n
B: MR, dB
C: IPD threshold, Hz, log scale
D: MR, dB
25
1,250
14
1,000
12
750
10
500
8
30
20
+
+
25
+
15
20
6
10
15
4
250
5
2
+
10
0
0
125
HI
HI
NHT
HI
NHT
MRspec MRspec MRtemp MRtemp
NHT
–2
NHT
HI
HI
NHT
MR = masking relase; spec = spectral; temp = temporal.
DISCUSSION
The mean scores of HI and NHT listeners in the RS test
did not differ. This is consistent with previous findings
[8, 10]. No correlation between RS score and hearing
thresholds was found here, which contrasts with an earlier study in which a significant negative correlation was
found [8]. In that study both the RS score and hearing
thresholds were also correlated with age, such that age
could have been the determining factor. Working memory could also influence the HI listeners’ ability to use
the HA. However, no correlation was found here between RS score and HA satisfaction.
No correlation was found between spectral and
temporal MRs in the F&T test and hearing thresholds
[9]. This finding was in contrast with an earlier study
[14]. Our study used a slightly different set-up aiming to
make the test more independent of test frequency,
which may partly account for the different findings.
The obtained significant difference between NHT and HI
listeners in temporal MR is consistent with previous
studies [7, 14, 15]. The lack of correlation with hearing
thresholds could indicate that temporal resolution is an
important non-audibility-related skill that should be
taken into account when making a hearing profile.
The obtained mean frequency limit for IPD detection was much lower than in other studies [10, 16]. TFS
TablE 2
95% confidence intervals
and p-values for correlation coefficients between
pure-tone average and all
tests (upper half) and international outcome inventory – hearing-aid subscales and all tests (lower
half). p < 0.05 is con­
sidered significant.
PTAlowa
PTAhighb
RS score
MRspec
MRtemp
IPD
MRHINT
95% CI
–
–
–0.38-0.35
–0.33-0.27
–0.53-0.03
–0.17-0.56
–0.73- –0.17
p-value
–
–
0.94
0.83
0.08
0.25
< 0.01
95% CI
–
–
–0.34-0.39
–
–
–
–0.37-0.36
p-value
–
–
0.9
–
–
–
0.99
95% CI
–0.05-0.64
–0.37-0.39
–0.50-0.25
–0.27-0.33
–0.19-0.41
–0.51-0.29
–0.79-–0.26
p-value
0.08
0.94
0.46
0.83
0.46
0.54
< 0.01
95% CI
–0.28-0.47
–0.53-0.20
–0.56-0.17
–0.28-0.34
–0.33-0.30
–0.09-0.64
–0.45-0.31
p-value
0.57
0.34
0.26
0.83
0.92
0.12
0.69
Audiogram
PTAlow:
PTAhigh:
IOI-HA
Introspection:
Interaction:
CI = confidence interval; HA = hearing-aid; high = high-frequency; HINT = hearing-in-noise test; IOI = international outcome inventory; IPD = interauralphase-difference; low = low-frequency; MR = masking release; PTA = pure-tone average; RS = reading span; spec = spectral; temp = temporal.
a) At 0.25, 0.5, 1 kHz.
b) At 2, 4, 6 kHz.
Dan Med J 63/10 October 2016
processing is known to decrease with age [17]. All listeners in our study were more than 40 years old, which
could explain the lower limits and the lack of group difference. The present results are consistent with previous
findings of no correlation between low-frequency hearing thresholds and IPD detection thresholds in HI listeners [10, 17]. Thus, the findings support that binaural TFSprocessing abilities decrease with age and are
independent of audibility.
MRHINT was significantly negatively correlated with
low-frequency hearing thresholds, suggesting that although low-frequency audibility may not be the sole factor, it does play a role in speech perception in fluctuating noise. However, audibility was not correlated with
HA satisfaction, whereas MRHINT was. This suggests that
pure-tone hearing thresholds are not a crucial factor for
HA satisfaction, while the ability to “listen in the dips” of
background noise might be a better predictor. By examining whether MRHINT was correlated with other psycho­
acoustic measures, we found a significant correlation
with temporal MR in the F&T test (r = 0.477; p = 0.029).
This is consistent with a recent study which also found
such a correlation [18]. Therefore, both temporal resolution and audibility may independently influence the ability to benefit from fluctuations in background noise, and
thus HA satisfaction.
Previous studies have also investigated how audibility was related to IOI-HA outcome. One study found a
positive correlation between hearing thresholds and
items 1 and 4 and a negative correlation between hearing thresholds and item 6 [13]. Another study found no
such correlations [19]. In contrast to the former study
[13], the latter [19] and the present study only included
listeners with sensorineural hearing loss, which may
partly explain the different findings. If, as found here,
hearing thresholds do not correlate with HA satisfaction,
it is questionable to use the audiogram as the only key
measure for HA fitting.
Finally, satisfaction in listening situations “conversation with one person”, “in a small group”, “in larger
groups”, and “outdoors” was previously found to be important to receive a high IOI-HA outcome [20]. This is
consistent with the present study’s finding that the abil­
ity to benefit from fluctuations in noise is related to IOIHA outcome. However, as many factors are known to influence IOI outcome, caution is advised when drawing
conclusions from the IOI-HA, and the questionnaire may
be too general to be directly related to specific psycho­
acoustic measurements.
CONCLUSION
The tested auditory profile confirmed that HI listeners
have difficulties in different hearing domains that are
not predictable from their audiogram. Specifically, tem-
d a n i s h m E d i c a l J O U R NAL 5
poral resolution and low-frequency hearing thresholds
were found to be related to speech recognition in fluctuating versus stationary noise. Hearing-impaired listeners,
who had a more limited intelligibility advantage from
fluctuations in the background noise, experienced
greater HA satisfaction. Neither hearing thresholds nor
other test outcomes were correlated with HA satisfaction. Measures of temporal resolution or speech perception in both stationary and fluctuating noise could be
relevant measures to consider in an extended auditory
profile. However, further large-scale studies are needed
to examine how such an extended clinical auditory profile should be related to HA fitting procedures. A more
objective evaluation of HA benefit would also be an important step forward.
CORRESPONDENCE: Nicoline Thorup. E-mail: [email protected]
ACCEPTED: 23 June 2016
CONFLICTS OF INTEREST: Disclosure forms provided by the authors are
available with the full text of this article at www.danmedj.dk
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